Extension of proposal of standards for intelligibility tests of Chinese speech: CDRT-tone

The published Chinese diagnostic rhyme test (CDRT) has been proposed as a standard method for evaluating the intelligibility of coded, synthesised or distorted Chinese speech over wired or wireless voice channels in a communication system. Inheriting the philosophy of the English context DRT test, the CDRT only assessed six groups of phonetic attribute distortion. However, pitch distortion is a highly important element for evaluating intelligibility of Chinese speech, which is characterised by Chinese tones, an important element of Chinese language which is absent in western languages. An extension to the CDRT named ´CDRT-tone´ for the intelligibility test of Chinese tones is proposed. The relative features of Chinese tones are outlined and the principles of choosing phonetic units for the proposed standard, CDRT-tone, are presented. Then the validity of the CDRT-tone is discussed. Finally, CDRT-tone was applied to evaluate the pitch performance of the GSM regular pulse excitation with a long-term prediction (RPE-LTP) coding algorithm.